Impeller with an abradable tip

ABSTRACT

An impeller for moving liquid through a pump system having a body, at least one vane extending from the body and capable of moving liquid through the system during rotation thereof, and a tapered, abradable tip extending from the vane wherein, during rotation of said body, the tapered end of abradable tip wears away in response to contact with the pump housing to produce a reduced amount of abradable material circulating through the system while providing nominal operational clearance between the tip and the housing to improve pumping efficiency.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority from U.S. Provisional Patent Application No. 60/611,456 filed on Sep. 20, 2004, and is hereby incorporated by reference herein.

FIELD OF ART

The invention relates generally to impellers for liquid pumps, and more particularly, to an impeller with an abradable tip for promoting greater pumping efficiency.

BACKGROUND OF THE INVENTION

Centrifugal pumps known in the art generally comprise an inlet pipe and an outlet pipe that are separated by a pumping chamber containing an impeller assembly. Typically, the impeller comprises a plate having a plurality of vanes that are radially spaced thereabout. The impeller is mounted on the end of a drive shaft that is driven by an external motor. When driven by the drive shaft, the impeller vanes transfer kinetic energy to the liquid in contact therewith. This kinetic energy causes pressure to build up, and the pressure causes the liquid to flow from the inlet pipe towards the outlet pipe.

In the operation of such centrifugal pumps, the liquid flow is generally effected by the design and size of the impeller, the design and size of the casing, the speed at which the impeller rotates, the design and size of the pump inlet and outlet and the like. One of the most critical elements of the design is the axial clearance distance between the impeller vane tip and the housing, wherein a small axial clearance is more efficient than a large axial clearance.

Pump impellers of the above arrangement have manufacturing and assembly advantages in that the components can be conveniently produced from stamped thin metals and easily assembled with minimum skill. However, such arrangements have been found to have inherent inefficiency problems. As the housing is stationary and the impeller rotates, the operational seal between the components typically involves maintaining a critical tolerance between the impeller vane tips and the housing. Typical low cost metal stamping processes make it difficult to maintain such close tolerances. Therefore, the clearance between the impeller vane and the housing is often much greater than necessary, thereby reducing efficiency of the pump.

Further, numerous fluid pumps operate in a closed system where the circulating fluid is not exchanged or adequately filtered. Therefore, any abraded material that enters the fluid must either be filtered out or accounted for so as not to harm the system during repeated circulation. As such, it is an object of the invention to introduce as little abraded material into the circulatory system so as to avoid any clogging or damage that may be caused by the constant circulation of such abraded material in a closed circulatory system.

Therefore, there is a need in the art to provide ever-decreasing axial clearance distances between the impeller vane tip and the housing to promote increased pumping efficiency while simultaneously accounting for abraded material in the circulatory system.

SUMMARY OF THE INVENTION

The axial clearance between the impeller vane tip and the pump housing pocket is critical for maximum pump efficiency, e.g. a small axial clearance is more efficient than a large axial clearance. Current pump practice is to set the nominal impeller clearance based on the tolerance stack of the impeller vane height, housing pocket depth, and impeller location when assembled to the pump to assure that no contact is made between the impeller and housing pocket. Because of the tolerance stack up of the components as described above, the impeller maximum clearance is often too large, thereby reducing pump efficiency.

As such, the invention makes use of a sacrificial or abradable wear tip on the impeller vanes to produce a minimum operational clearance between the impeller and the housing. While such an abradable tip can be constructed in numerous manners, the goal is to provide impeller pump vanes that through use will wear against the pump housing to provide a minimum axial clearance therebetween. The abradable wear tips are designed to not damage the impeller or the pump housing, but provide a superior nominal clearance over the prior art, thereby improving efficiency. Further, the abraded material from the vanes is to be kept to a minimum to avoid damage to or clogging of the circulatory system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a centrifugal pump assembly.

FIG. 2 is a cross-sectional view of the centrifugal pump assembly of FIG. 1 shown along lines 1-1.

FIG. 3 a is a cross-sectional, enlarged view of the vane tip of the impeller of FIG. 1 after the abradable tip has been worn.

FIG. 3 b is a cross-sectional view of a first embodiment of an abradable vane tip of the invention.

FIG. 3 c is a cross-sectional view of the abradable van tip of FIG. 3 b after wear.

FIG. 3 d is a cross-sectional view of an alternate embodiment of an abradable vane tip.

FIG. 3 e is a cross-sectional view of yet another alternate embodiment of an abradable vane tip.

FIG. 3 f is a cross-sectional view of still another alternate embodiment of an abradable vane tip.

FIG. 3 g is a cross-sectional view of another alternate embodiment of an abradable vane tip.

FIG. 3 h is a cross-sectional view of yet another alternate embodiment of an abradable vane tip.

FIG. 4 is a perspective view of the impeller of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

While the invention is described with reference to the preferred use of the invention as used with a centrifugal water pump of an internal combustion engine, it should be clear to those skilled in the art that the invention could be utilized for any number of liquid circulatory applications whether closed or open systems. Therefore, neither the present description of the preferred use nor the present description of the several alternate embodiments should limit the scope of the invention apart from the invention as specifically recited in the appended claims.

Now referring to the drawings, and particularly to FIGS. 1 and 2, a single stage centrifugal pump 10 is shown in partial cross-section. The pump 10 is positioned between an inlet opening 12 and an outlet opening 14 to force liquid from the inlet opening 12 through the outlet opening 14. The pump 10 includes an impeller 16 that is mounted to the end of a drive shaft 18 that in turn is connected to a hub 20. The drive shaft 18 is rotatably movable within a pump housing 22 through bearings 24. An engine accessory drive belt (not shown) drives the hub 20, which in turn drives the shaft 18, which in turn drives the impeller 16 within the pumping chamber 26 to circulate the fluid, in this case water, through the system. The first embodiment of the impeller is shown in FIG. 4.

The pumping chamber 26 is defined by pump housing 22 and the pump closure 28. The pump closure, depending upon the configuration and application used, could be an engine block, front cover, pump closure plate or casting, or the pump housing itself. Therefore, when the impeller 16 rotates within the pumping chamber 26, liquid is forced from the inlet 12 through the outlet 14. The impeller 16 includes a plate 30 having a plurality of vanes 32 spaced apart thereon. These vanes 32 come in close proximity to the pump closure 28 as best shown in the area of FIG. 1, encircled as 3A, designating FIG. 3A. A clearance 34 is shown in FIG. 3A between the vane 32 and the pump closure 28.

The invention is directed to providing an impeller 16 having a superior nominal clearance 34 over the prior art to improve pumping efficiency. As such, an abradable vane tip 36 is provided that wears against the pump housing to provide a minimum operational clearance between the impeller 16 and the surface it may engage, likely the pump closure 28. It is presently desired that a high lubricity polymer be utilized for the tip 36, however, other materials that easily wear against the pump closure or housing could be used. Further, because the invention is being used in the preferred use in a closed fluid circulatory system of an internal combustion engine, the abraded material must be kept to a minimum so as not to interfere with the operation of the system. There are several configurations described below that achieve this result. None of these embodiments is presently preferred, however, each will be described in detail with reference to the drawings. However, it should be realized that numerous other configurations could be used according to the invention and as covered by the appended claims but are not disclosed herein for the sake of simplicity.

As shown in FIGS. 3 b, the abradable tip 36 extends from the impeller vane 32 and wears against the pump closure 28 during the initial impeller rotation. As shown in FIG. 3 c, such wear creates an operational minimal clearance 34 between the vane 32 and the pump closure 28. This operational minimum clearance 34 should be as small as possible given the dimensions of the impeller and pump operations. Further, because the impeller 16 shown in FIGS. 3 b and 3 c is tapered to a point, only a small amount of abraded material will be introduced within the circulatory system.

Other alternate embodiments are shown in FIG. 3 d (“round nose” configuration), FIG. 3 e (“arrowhead nose” configuration), FIG. 3 f (“trapezoidal nose” configuration), FIG. 3 g (“square nose” configuration), and FIG. 3 h (“hollow-ground nose” configuration). Each of these configurations is designed to produce an impeller manufactured to varying specifications that can be “self-tolerancing” when operated within the system.

Clearly the shape of the tip 36 plays a critical role in the amount of abraded material circulating through the system. While keeping such abraded material flowing through the system at a minimum is important, other factors may be considered in developing an impeller tip 36 shape. For example, a tip 36 having a tapered shape can minimize friction when the impeller tip 36 contacts the pump closure 28 while not being easily broken. Further, such impellers having such a shape would be distinctly easier to produce and not require exact tolerances so long as the impeller would be “self-tolerancing” when operated within the system. Also, while the preferred use of the invention discloses a centrifugal pump having axially extending vanes, it should be clear to those skilled in the art that the invention could be use with impellers having a radially extending vanes or any other vane constructions wherein the vane contacts a housing or closure member.

While the invention has been described with reference to the preferred use of utilizing the invention with an automotive water pump, obviously other embodiments, modifications, and alternations could be ascertained by one skilled in the art upon reading the present disclosure. The invention is intended to cover these other embodiments, modifications, and alterations that fall within the scope of the invention upon a reading and understanding of this specification. 

1. An impeller for moving liquid through a system, said impeller comprising: a body capable of rotation within a pump housing; at least one vane extending from said body and capable of moving liquid through a system during rotation of said body; and an abradable tip extending from said vane and having a tapered end; wherein, during rotation of said body, said tapered end of said abradable tip wears away in response to contact with said pump housing to produce a reduced amount of abradable material circulating through said system while providing nominal operational clearance between said tip and said housing to improve pumping efficiency.
 2. The impeller of claim 1 wherein said system is a circulatory system.
 3. The impeller of claim 2 wherein said circulatory system is a closed circulatory system.
 4. The impeller of claim 3 wherein said fluid is water.
 5. The impeller of claim 4 wherein said closed circulatory system is the water pump system of an internal combustion engine.
 6. The impeller of claim 5 wherein said impeller is manufactured from plastic.
 7. An impeller for moving liquid through a closed circulatory system, said impeller comprising: a body capable of rotation within a pump housing; at least one vane extending from said body and capable of moving liquid through a closed circulatory system during rotation of said body; and an abradable tip extending from said vane and having a tapered end; wherein, during rotation of said body, said tapered end of said abradable tip wears away in response to contact with said pump housing to produce a reduced amount of abradable material circulating through said closed circulatory system while providing nominal operational clearance between said tip and said housing to improve pumping efficiency.
 8. The impeller of claim 7 wherein said liquid is water.
 9. The impeller of claim 8 wherein said closed circulatory system is a water pump system of an internal combustion engine.
 10. The impeller of claim 9 wherein said impeller is manufactured from plastic.
 11. The impeller of claim 10 wherein said pump is a centrifugal pump. 